analysis and optimization of engine mounting bracket · 2018-09-27 · mounting bracket as well as...
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International Journal of Scientific Engineering and Research (IJSER) www.ijser.in
ISSN (Online): 2347-3878, Impact Factor (2014): 3.05
Volume 3 Issue 5, May 2015 Licensed Under Creative Commons Attribution CC BY
Analysis and Optimization of Engine Mounting
Bracket
Monali Deshmukh1, Prof. K R Sontakke
2
1Student of ME CAD/CAM, Pankaj Laddhad Institute of Technology and Management Studies, Buldana, Sant Gadge Baba Amravati
University
2Department of Mechanical Engineering, Pankaj Laddhad Institute of Technology and Management Studies, Buldana, Sant Gadge Baba
Amravati University
Abstract: The engine mounting plays an important role in reducing the noise, vibrations and harshness for improving vehicle ride
comfort. The brackets on the frame that support the engine undergo high static and dynamic stresses as well as huge amount of
vibrations. Hence, dissipating the vibrations and keeping the stresses under a pre-determined level of safety should be achieved by
careful designing and analysis of the mount brackets. Keeping this in mind in this paper, Static Analysis, model analysis of engine
mounting is done as well as harmonic response analysis of bracket as a part of dynamic analysis is performed with the FEA software
package ANSYS 15.0.The existing model is optimized and a novel model was proposed to reduce the weight of the rib of the engine
mounting bracket as well as the harmonic response in term of acceleration is checked to ensure that the proposed model will not result in
to noisy operation. The results of the stresses, deformations and harmonic response for the both models of the engine mounting bracket
were compared to each other. With the proposed model of the engine mounting bracket 12.5%weight reduction is achieved maintaining
an acceptable level of yield stress and harmonic response.
Keywords: Mounting Bracket, Static Analysis, Dynamic Analysis, Optimization
1. Introduction
Design engineers always aims at improvement in each and
every part of automobile system. Automobile industry
continued improving since from many years with the efforts
conducted for the purpose of modification of the mechanical
parts of vehicles in order to improve their performance and
vibration response. These characteristics have a vital impact
on the mechanical performance of the overall system balance.
In addition, redesigning the mechanical models play an
important role in improving the sustainability of the system
against the resultant stresses and strains, therefore, significant
consideration should be taken for this when designed by
engineers.
In an automotive vehicle, the engine rests on brackets which
are connected to the main-frame or the skeleton of the car.
Hence, during its operation, the undesired vibrations
generated by the engine and road roughness can get directly
transmitted to the frame through the brackets. This may cause
discomfort to the passenger(s) or vibrations might even
damage the chassis. Also, at high operating frequencies noise
becomes a serious concern. Hence, damping of these engine
vibrations and checking the harmonic response of bracket
while designing is essential. The Noise & Vibration Harness
analysis (or NVH) is one the most important considerations
in automotive designing today. If the brackets have their
resonance frequencies close to the operating engine
frequencies, then the large amplitude of vibration get
generated which may cause its fatigue failure or breakage,
thus reducing its estimated or desired life. And if the
harmonic response values of bracket is more than acceptable
range it results in to generation of noise. Hence it is required
to check the harmonic response of designed bracket.
Vibration damping can be either provided by using separate
dampers (anti-vibration mounts) or by suitably deciding the
material and dimensions of the brackets. Moreover, the
brackets also undergo deflection under static and dynamic
loads. This deflection should be under permissible limits.
Some vehicle required to be highly maneuverable and quick
with high rates of acceleration and deceleration, Hence the
mounting of the engine should be well constrained and the
mount brackets need to be light-weight and designed to
safely bear the inertial loads and maximize vibration
transmission. The response of vibrating system can be in the
form of displacement, velocity, acceleration or sound. These
have to be kept under safe or acceptable limits while
designing. Here the response in term of acceleration is taken
into focus. Static structural and model analysis of bracket is
done and results are used for analyzing harmonic response of
bracket. Existing bracket design is optimized. The modified
designed has been reanalyzed using FEA before finalization.
2. Methodology
In this paper, Static structural and Model analysis were used
to determine the characteristics of the engine mounting
bracket. And Harmonic response analysis is done to check
the response of structure in terms of acceleration. To obtain a
comprehensive design, the existing model is modified by
changing its rib geometry. Again the modified bracket had
undergone same analysis procedure and the results were
compared for both the designs.
The purpose was to determine the stresses, deformations and
harmonic response of bracket that affect's on the engine
mounting brackets and to optimize the design that make a
reduction in the weight of the rib of the engine mounting
models. Work has been carried out with ANSYS 15.0
software.
Paper ID: IJSER15209 131 of 136
International Journal of Scientific Engineering and Research (IJSER) www.ijser.in
ISSN (Online): 2347-3878, Impact Factor (2014): 3.05
Volume 3 Issue 5, May 2015 Licensed Under Creative Commons Attribution CC BY
3. Analysis of Engine Mounting Bracket
3.1 Existing Model of Engine Mounting Bracket:
Figure 1: Engine mounting bracket
The model shown above is taken for analysis. The existing
model of an engine mounting bracket is a sheet metal part.
And it has less curvatures and the thickness of the part is
uniform unlike model created by casting procedure. Hence
for analysis purpose surface model of bracket was imported
as shown in figure 1 instead of solid model.
3.1.1Boundary conditions And Properties
The engine mounting bracket to be analyzed is a part of
engine weighing 170kg. Torque used as an input is 1×105 N-
mm. Isolators stiffness is 200 N/mm in Y direction and
100N/mm in X and Z directions. Idling: 5000 rpm and
maximum: 9000 rpm. Existing model is made up of structural
steel with following properties:
Young’s modulus =2e5 Mpa
Poisons ratio = 0.33
Density =7850 kg/m3
Yield strength = 270 Mpa
Figure 2: Boundary conditions
3.2 Static Structural Analysis
A static structural analysis is the analysis displacements,
stresses, strains and forces on structure or a component due to
load application. The structures response and loads are
assumed to vary slowly with respect to time. There are
various types of loading that can be applied in this analysis
which are externally applied forces and pressures, and
temperatures.
Figure 3: Total deformation
The total deformation is 52.964mm for existing bracket as
shown in figure 3
Figure 4: Von-Mises stress
Figure 4 shows equivalent Von-Mises stresses. Von- Mises
stresses are resultant stresses or yield strength of material,
after which deformation starts. Maximum value of stress is
125.25Mpa and the color plot shows the portion where the
maximum amount of stress acts.
3.3. Modal Analysis
Modal analysis determines the vibration characteristics of a
structure or a particular component in the form of natural
frequencies and mode shapes. From this analysis we can do
more detailed dynamic analysis such as transient dynamic
analysis, harmonic analysis or spectrum analysis. The natural
frequencies and mode shapes are important in the design of a
structure for dynamic loading conditions. In this analysis,
only linear behavior is valid. Damping is not considered and
applied loads are ignored in modal analysis. A static
structural analysis is required first for performing pre stressed
modal analysis. This analysis was done to find out the natural
frequencies and mode shapes of the bracket.
The operating frequency range is 250Hz-450Hz.
Paper ID: IJSER15209 132 of 136
International Journal of Scientific Engineering and Research (IJSER) www.ijser.in
ISSN (Online): 2347-3878, Impact Factor (2014): 3.05
Volume 3 Issue 5, May 2015 Licensed Under Creative Commons Attribution CC BY
Figure 5: Mode 12
Figure 5 shows twelfth mode of vibration. The frequency of
vibration for this particular mode is 284.4 Hz. Figure 6 shows
thirteenth mode of vibration and the frequency of vibration
for this mode is 377.36Hz.
Figure 6: Mode 13
Figure 7: Mode 14
Figure 7 shows fourteenth mode of vibration and here bracket
is subjected to maximum deformation at the end section of its
base. The frequency of vibration for this particular mode is
408.52 Hz.
Figure 8 shows fifteenth mode of vibration. The frequency of
vibration for this particular mode is 408.52 Hz.
Figure 8: Mode 15
3.4 Harmonic Response Analysis
3.4.1Definition of Harmonic Response Analysis
Any sustained cyclic load will produce a sustained cyclic
response (a harmonicresponse) in a structural system.
Harmonic response analysis gives you the ability to predict
the sustained dynamic behavior of your structures, thus
enabling you to verify whether or not your designs will
successfully overcome resonance, fatigue, and other harmful
effects of forced vibrations.
3.4.2 Uses of Harmonic Response Analysis
Harmonic response analysis is a technique used to determine
the steady-state response of a linear structure to loads that
vary harmonically with time. The idea is to calculate the
structure's response at several frequencies and obtain a graph
of some response quantity (usually displacements) versus
frequency. "Peak" responses are then identified on the graph
and stresses reviewed at those peak frequencies.
Result from model analysis is used as input for calculating
harmonic response. Acceleration of 3×G = 3×9806.6 = 29420
mm/s2 is used. The engine operating frequency range is 250
Hz to 450Hz, modes 12 to 15 are within engine operating
frequency range. Hence mode shape 13 is chosen and its
maximum deformation location is used for checking response
output.
Figure 9: Harmonic response graph
Results were plotted for harmonic response of bracket with
40 solution intervals. Figure 9 shows graph between
amplitude (mm/s2) and frequency (Hz). Graph shows 40
points for which response is calculated. For engine operating
Paper ID: IJSER15209 133 of 136
International Journal of Scientific Engineering and Research (IJSER) www.ijser.in
ISSN (Online): 2347-3878, Impact Factor (2014): 3.05
Volume 3 Issue 5, May 2015 Licensed Under Creative Commons Attribution CC BY
frequency range 250 to 450 Hz the amplitude varies from
28443 mm/s2 to 29713 mm/s
2.
4. Optimization of Engine Mounting Bracket
4.1 Suggested Model:
Figure 10: Suggested model
The model shown in figure 10 is optimized model. After
studying the result of analysis of engine mounting bracket,
certain design changes have been made here. Here in this
optimized model, geometry of rib which connect two faces of
bracket is changed. Suggested optimized model has a rib with
reduced cross sectional area than previous model. Hence it
results in to weight reduction of overall structure.
But to finalize the optimized design, it is needed to analyze
the bracket with same boundary conditions applied to the
previous model. And if the results obtain fall within the limits
obtained from analysis of initial (original) design, then only
the optimized design can be finalized.
4.2 Static Structural Analysis
Static structural analysis is performed for the optimized
design with same boundary conditions and input values.
Figure 11: Total deformation
Figure 12: Von-Mises stress
4.3 Model Analysis
This analysis was done to find out the natural frequencies and
mode shapes of the bracket.
Figure13: Mode 12
Figure 14: Mode 13
Figure 15: Mode 14
Paper ID: IJSER15209 134 of 136
International Journal of Scientific Engineering and Research (IJSER) www.ijser.in
ISSN (Online): 2347-3878, Impact Factor (2014): 3.05
Volume 3 Issue 5, May 2015 Licensed Under Creative Commons Attribution CC BY
Figure 16: Mode 15
4.4 Harmonic Response Analysis
Result from model analysis is used as input for calculating
harmonic response. Acceleration of 3×G = 3×9806.6 = 29420
mm/s2 is used. As the engine operating frequency range is
250 Hz to 450Hz, mode shape 13 is chosen and its maximum
deformation location is used for checking response output.
Figure 5.13: Harmonic response graph.
Results were plotted for harmonic response of bracket with
40 solution intervals. Figure 5.13 shows graph between
amplitude (mm/s2) and frequency (Hz). Graph shows 40
points for which response is calculated. For engine operating
frequency range 250 to 450 Hz the amplitude varies from
27990 mm/s2to 29922 mm/s
2.
5. Result and Discussion
Result obtained from static structural analysis, model analysis
and harmonic analysis are listed and compared with each
other in this section.
Table 6.1: Comparison analysis result Initial Bracket Optimized Bracket
Total deformation (max) 52.964 mm 53.041 mm
Von-Mises stresses (max) 125.25 Mpa 142.53 Mpa
Harmonic response
(mm/s2)
28443 to 29713
27990 to 29922
Weight of bracket
2 kg
1.75 kg
Engine operating frequency range lies between 250 to 450 Hz
and the amplitude varies from 28443 to 29713 mm/s2 for
initial un-optimized bracket. For optimized bracket amplitude
varies from 27990 to 29922 mm/s2.
Response of optimized structure in term of vertical
acceleration shows slightly greater value of maximum
acceleration than initial bracket design, but it shows very
little difference. The resultant harmonic response of
optimized structure is well within safe limit. Hence it is
acceptable. But if the amplitude shows noticeable deviation it
results into noisy operation.
With comparison of all the resultant values it can be seen that
deformation values of optimized bracket are nearly similar as
that of initial bracket. Stress value for optimized bracket is
slightly greater than that of initial bracket, but it lies within
maximum permissible limit range of bracket hence is
acceptable. And the values of harmonic response in term of
vertical acceleration for optimized bracket also nearly match
with initial bracket and hence the value is acceptable.
6. Conclusion
The optimization of engine mounting bracket is attempted by
applying certain changes in its design and shape. After
comparison of results obtained from analysis performed, it is
concluded that the optimization attempted is found
successful. And with the optimization done in the bracket it is
found that as the cross sectional area of rib is reduced the
overall weight of the bracket is also reduced. The modified
design of bracket is obtained which is 12.5% lighter by
weight than initial on-optimized bracket. This results in
material saving, and overall cost reduction.
Also it is confirmed by harmonic analysis that the harmonic
response of modified bracket is within safe limit. So the
chances of noisy operation of structure due to its design are
minimized.
References
[1] SahilNaghate and Sandeep Patil (2012), “Modal
Analysis of Engine Mounting Bracket Using FEA”,
International Journal of Engineering Research and
Applications (IJERA), Vol. 2, 1973-1979.
[2] K A Zakaria, S Abdullah, M J Ghazali, M Z Nuawi, S M
Beden and Z M Nopiah (2013) “Fatigue Strain Signal
Behavior and Damage Assessment of an Engine Mount
Bracket”, Journal of scientific and Industrial Research
Vol. 73, February 2014, pp 112-116.
[3] Umesh Ghorpade, D.S.Chavan, Vinaay Patil and
Mahendra Gaikwad,“Finite Element Analysis and
Natural Frequency Optimization of Engine Bracket”,
International Journal of Mechanical and Industrial
Engineering (IJMIE) ISSN No.2231-6477, Vol-2, Iss-
3,2012
[4] Pramod Walunje and prof. V. K. Kurkute (Dec 2013)
“Optimization of Engine Mounting Bracket Using FEA”,
PARIPEX – International journal of research.
[5] Pavan B. Chaudhari and Dr. D. R. Panchagade (2012),
“Comparison of Magnesium, Aluminium and Cast Iron
to obtain Optimum Frequency for Engine Bracket using
Finite Element Analysis”, International Journal of
Paper ID: IJSER15209 135 of 136
International Journal of Scientific Engineering and Research (IJSER) www.ijser.in
ISSN (Online): 2347-3878, Impact Factor (2014): 3.05
Volume 3 Issue 5, May 2015 Licensed Under Creative Commons Attribution CC BY
Engineering Research andApplications (IJERA) , Vol. 2,
1016-1020.
[6] Sameer U. Kolte, Dvid Neihguk, and Abhinav Prasad,
“Structural Durability Analysis of Powertrain Mounting
Bracket”, excerpt from the Poceedings of the 1012
COMSOL conference in Bangalore.
[7] M V Aditya Nag, “Material Selection and Computational
Analysis on DOHC V16 Engine’s Mounting Bracket
Using COMSOL Multiphysics Software” excerpt from
the Poceedings of the 1012 COMSOL conference in
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[8] Haval Kamal Asker, “Comparison of The Mechanical
Properties Of Different Models of Automotive Engine
Mounting” ARPN Journal of Engineering and Applied
Sciences, Vol. 8, no. 6, June 2013
[9] P.D. Jadhav, Ramakrishna, “Finite Element Analysis of
Engine Mount Bracket” International Journal of
Advancement in Engineering Technology, Management
and Applied Science, Vol. 1, September 1014.
Author Profile
Monali Deshmukh received the B.E. degree in
Mechanical Engineering from Anuradha
Engineering College, Chikhli affiliated to Sant
Gadge Baba Amravati University, Amravati in
2013. She is a research scholar, presently
pursuing ME 2nd
year from Pankaj Laddhad Institute of
Technology and Management Studies, Buldana affiliated to
Sant Gadge Baba Amravati University, Amravati.
Paper ID: IJSER15209 136 of 136
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